In a small bowl, mix together ground cumin, chili powder, garlic powder, onion powder, smoked paprika, salt, and black pepper.
Rub the spice mixture evenly over the beef chuck roast.
Heat olive oil in a large skillet over medium-high heat. Sear the beef roast on all sides until browned, about 3-4 minutes per side.
Place the seared beef roast in the slow cooker.
Add the chopped onion, minced garlic, and beef broth to the slow cooker around the beef.
Pour 1 cup of the red enchilada sauce over the beef.
Cover and cook on low for 6 hours, or until the beef is very tender and easily shredded.
Once cooked, remove the beef from the slow cooker and shred it using two forks.
Preheat the oven to 350°F (175°C).
In a 9×13 inch baking dish, spread a thin layer of enchilada sauce on the bottom.
Place one tortilla on the sauce layer, then add a layer of shredded beef, a sprinkle of chopped onions, and a mix of cheddar and Monterey Jack cheese.
Repeat layering with tortillas, beef, onions, cheese, and enchilada sauce until all ingredients are used, finishing with a cheese layer on top.
Cover the baking dish with aluminum foil and bake for 20 minutes.
Remove the foil and bake for an additional 10 minutes, or until the cheese is melted and bubbly.
Remove from oven and let the enchilada stack rest for 5 minutes before slicing.
Garnish with chopped fresh cilantro and serve with sour cream on the side.